Questionable Cylinder Head Resurfacing Job

Cody Diagnostician Illinois Posted   Latest   Edited  
Resolved
Parts
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2016 Chevrolet Trax LS 1.4L (B LUV) 6-spd (6T40) — 3GNCJNSB3GL243876

Got this cylinder head back from a different machine shop that we have never used before. the gasket surface is scratched pretty bad. the machine shop owner said he used a belt sander to remove .005" and he's been doing it this way for 12 years with no comebacks. i call bullsh%t. several of the scratches can be felt with my finger nail which i've heard that is too deep. wondering what you guys think if we should give this a shot to see if it seals. i am thinking a solid no.

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Darren Owner/Technician
Arkansas
Darren
 

Well, if the scratches you are referring to are the ones 90 degrees to the length of the head then those were caused after sanding. Likely cause is transporting the head flat or sliding the head. As for using a belt sander, I have to confess I have done it in the past on occasion. Done correctly you can achieve a correct surface finish (RMS) and a level surface withing specs. When I have had to…

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Ronald Owner/Technician
California
Ronald
 

Wow…a belt sander to resurface a head especially on an aluminum head. I am completely uncomfortable with that. I do believe for aluminum heads it takes very specific finishes to seal them up with the tri layer gaskets. Machine shops are a gamble anymore. I think the guys that knew their stuff are gone or hanging onto old ideas that do not work or they are young guys that are lazy and have no…

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Caleb Diagnostician
Indiana
Caleb
 

Buy new head from the dealer. They are usually in stock. Do not use that thing.

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Michael Owner/Technician
New Jersey
Michael
 

Nope.

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Michael Mobile Technician
Utah
Michael
 

Using a flat sander is a common practice. I have not had any issues with that method. It looks like he should have gone a touch deeper as the color is not uniform showing what appears to be a high spot near the end of the head.

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Mark Engineer
Colorado
Mark
 

Ditto on the “nope”. Get another head. Hard to believe he’s still in business.

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Marvin Mechanic
Mississippi
Marvin
 

Head must be flat so I would not trust it ..ours resurfaces from one end to the other on some type of milling machine ..if it’s comes back with head gasket leaking who pays for it ? You right

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Matthew Owner/Technician
Oregon
Matthew
 

I haven't looked this up but does it take MLS gaskets or the old style composite ones? If it's the multi layer gasket this absolutely will not work. If it's composite it should be fine. There's a smoothness rating for MLS gaskets (RA- Roughness average) that really needs to be followed for a job that's going to last. If you are using a machine shop that doesn't know about RA and can measure it…

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Todd Owner/Technician
Virginia
Todd
 

Sorry man but that looks pretty bad. I hope you are not out a lot of money.

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Bill Owner
Maryland
Bill
 

Cody, I know there are shops that use them but I refuse. A bunch of years ago I had an equipment sales rep that kept bugging me to try one. Finally I got so sick of him that I had him leave it and I gave it a try. My biggest issue with it was no matter how hard I tried I could not get it to cut the same amount off the entire length of the head. It always wanted to cut more of the leading edge…

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Michael Technical Support Specialist
California
Michael
 

That's old school. If it's a soft, composite gasket, it'll probably work. MLS, no way. Very fine surfacing (using a mill?) has been around for a long time, may be 20 years or more. He hasn't had any comebacks because his customers find a modern machine shop after visiting him.

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Tony Technician
California
Tony
   

Interesting issue. ‘Belt sander' can mean a few things. Pics, first and second are obviously OUT. The third is common equipment for some shops and have been in use for decades. From what I see, you could probably get away with a regular type head gasket, but not if an MLS gasket is being used. In the future, I would find a shop that mills the heads, preferably with a cutter but an abrasive disk…

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Mike Engineer
California
Mike
 

Using a belt sander is a job you can do at home and most of the time you will get away with it on regular small block gasoline engines. But try this on a high compression diesel engine and you are out of luck so best is to bring it to a machine shop and let it resurface on a precision resurface machine. You got to a business who does not high quality work but it might still work for you. Is like…

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Ted Owner
Texas
Ted
   

I would not trust that surface to be flat or finish acceptable for a MLS gasket. As him what the finished RA is. If you have a large “flat” piece of granite or marble you could check/finish the surface with 600 grit and water. Use sharpie to mark between cylinders and length of head to see if there are any low spots. If not, get a replacement. Correction - I looked at my setup (been a while…

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Glenn Owner/Technician
Texas
Glenn
   

Hi Cody, If the surface is not a polished finish, do not use it. Lesson learned? This shop is probably 40 years behind the times and using outdated equipment. 12 years and no comebacks? Probably because they have been doing this kind of work for used car lots and DIY hacks who flip cars for a quick buck. If they are AERA certified, they need their certification revoked. To save this head, I…

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Paul Owner/Technician
California
Paul
 

Hi Cody, Around 20 years ago we used to use a platen grinder (big ass belt sander) to resurface cylinder heads. It was before we knew better and all gaskets were composite back then, at least on the cars we were fixing. It can “work”. However, there are some problems. I don't know Chevy at all, but I'm guessing that nearly all cars use MLS gaskets these days. If that's the case with your…

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Cody Diagnostician
Illinois
Cody Resolution
 

Thanks for the input guys. Been working on cars for about 16 years and ive never seen one this bad from a machine shop. The problem is our old tried and true machine shop we used for decades closed down and they did very good work with a good warranty. We are very limited on the machine shops in our area(40 minutes away for the closest one). The machine shop we have been using have the proper…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Cody, Like I mentioned before, this head can be saved. It will take about an hour slowly working it evenly with a rigid file board and fine sandpaper. Most body supply shops, or NAPA can get you what is needed. I have saved a few like this over the years. It just takes patience. For good measure, it may pay to lap in the valves just to be sure there are no issues there. Many machine shops…

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Marvin Mechanic
Mississippi
Marvin
 

Trust your first impression..you will have to stand behind it ..who pays the next time .do you have time to do it again .?a belt sander does not take off material the same as a milling machine ..Every time the belt goes in a hole and come out it takes off more material than staying on a flat surface ..the oldest shop in our area the Owner is in 70 ties and we will be without one in our area also…

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David Owner/Technician
Alberta
David
 

I have seen far worse. If it is flat, those tiny scratches will not be a big deal. It is best to have a finish with less scratching but they are not where you are likely to have any issues. You might see some miniscule coolant seepage but that would stop likely after the first couple of heat cycles.

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Zeb Diagnostician
California
Zeb
 

A wood working belt sander or like the linked tool? youtu​.​be/_X091HmGt7M

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Mark Diagnostician
Ohio
Mark
 

We used to use a resurface table years ago with no trouble which was essentially a sanding belt on an actual table and you weighed down the head to achieve a nice surface but never an actual hand held belt sander.

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Paul Mechanic
Illinois
Paul
   

He/she is the professional for the services you contracted for, just like we are for the services we provide. As long as machinst will put his money where his mouth is- pay for you to do it again if it fails, including any consumable materials to do job again, use it. That will put him in check and get it in writing. Otherwise, find another shop or head. Just preface your concerns with customer…

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Marlin Technician
Oregon
Marlin
 

Absolutely not! That is stupidity on the lose!

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Bill Owner
Maryland
Bill
   

I know this has run its course but I just want to add something. The surface finish on this head is probably fine. Most guys do not have a clue as too how “rough” is acceptable for most gaskets including mls. I am one of the few shops that actually has a Profilometer to measure surface finish and you would be amazed at how “rough” an acceptable finish can be. The finish on the head shown will…

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Marlin Technician
Oregon
Marlin
   

I have seem some surprisingly rough and inconsistent OE finishes, but nothing even close to what he has, even on old engines with composite gaskets. I wondering if you are seeing the detail in his photos. It is worse than exhaust manifold flanges.

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Darren Owner/Technician
Arkansas
Darren
 

Bill, I am glad you brought this up The human eye can easily discern 0.010" once taught the basics and with proper training 3 to 5 thou. without expensive tools. Most people can barely muster 0.010" Aside from being a tech I also make things on my lathes and mills. I have hand scraped to within 0.001 in minimal time and 0.0002 with effort. Some of the finest machines built were “hand worked”…

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David Owner/Technician
Alberta
David
 

Absolutely correct Bill. I recognize you as being very experienced and an expert . Very few of us on these forums work or have worked with this kind of thing, multiple times, every day Far too many of us will comment regarding these things without really having good information & experience or maybe even disregard data and facts. This finish spec. is not so easy to define without…

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Stephen Technician
Tennessee
Stephen
 

I regret that I can only give +1, once,(but, I tried).

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Tony Technician
California
Tony
   

Good points, D. Robin. Let's recap. We have 27 posts on the OP's request for info on several pictures and comments about using a machined head with an unknown gasket type that really only requires matching the surface roughness with head gasket requirements using specs that nobody mentioned possibly needing numbers from a profilometer that's not available to read that head. So, Cody, what are…

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Marlin Technician
Oregon
Marlin
 

Unknown gasket type? Why do you conclude that?

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Tony Technician
California
Tony
 

Didn't see it mentioned. Where did I miss that?

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Marlin Technician
Oregon
Marlin
 

If you didn't know already, you could have easily looked it up.

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Tony Technician
California
Tony
 

Granted, I could have looked it up if I was making a decision on what I'm doing, but I have no idea what Cody is up to unless he tells me and I usually won't make a call for other techs on a best guess.

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David Owner/Technician
Alberta
David
 

So since Cody did not tell us what gasket type, I looked it up. It is multilayer type. I note this manufacturer (FelPro) seems to have covered the likelihood of some imperfections such as the photos of the head shown. It is of course important to have the whole story with these things. Tony's post seems clear to me in the big picture idea to consider of a lot alarmist posts without all of that…

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Marlin Technician
Oregon
Marlin
 

No, he didn't mention the type, but that is readily available info and common professional knowledge. Just a typical MLS. Fel-Pro does put extra sealing material on some of theirs, which likely helps, if they work as well in reality as the theory. To risk the repair on a resurfacing job that clearly does not meet industry standards is unprofessional.

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David Owner/Technician
Alberta
David
 

Marlin, no I am not giving you this one so easily. How can you say the resurfacing job does not meet industry standards? We clearly do not know for certain without a surface meter and flatness check. Calling out the machine shop is not fair without documentation to support why. If you do not approve of the procedure, that is your personal preference and not necessarily due to the head being…

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Marlin Technician
Oregon
Marlin
 

By experience, from interaction with professionals, and by reading literature. Why don't you call a few automotive machine shops and equipment suppliers and ask them what type of surfacing is the standard for aluminum alloy cylinder heads with MLS gaskets? If you do this, not specifically contacting the most unprofessional businesses that you can find, you will confirm what I stated.

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Jesse Engineer
Missouri
Jesse
 

That's pretty rough, all least it's parallel with the length of the head. It might last 5-10k miles with an MLS gasket. One, at least its flat now. It just needs some touchup. Which, if you'r willing to put in some elbow grease, you can fix it. Ford calls out a mirror finish basically on some of their heads. i think that's a little excessive for most situations. i do my own because of the…

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Kevin Educator
California
Kevin
 

Justification for substandard practices always seems to start with: “I've been doing it this way for XX years". Whenever a Technician's best or only justification for their methods sounds similar to that, it's a safe bet they are the reason our industry has the reputation it does… JMO

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Off Topic
Michael Owner/Technician
New Jersey
Michael
 

The bottom line here is twofold. - Do you really need a comeback? - Can you with confidence put your name/reputation on the line with this resurfacing job? If the answer to either is no, you should know what to do.

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David Owner/Technician
Alberta
David
 

Michael, none of us needs comebacks due to something inferior. By what standard is a tech supposed to use to say this job was not acceptable? If you are using a machine shop to do something you cannot perform yourself, then you need to be able to trust them. If you don't understand what they are doing and are not satisfied with their answers, don't use them. If you don't trust them for good…

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Jesse Engineer
Missouri
Jesse
   

I would have to disagree with you on that. Back in the day when cars were simple, 50's-70's, everyone took pride in their work. There was craftsmanship in ones work. You could trust someone to do their job to the best of their ability and a greenhorn kid or adult would work their way up to more critical task. A standard socket set, wrenches and a flat head screwdriver would take apart about…

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Tony Technician
California
Tony
 

Unfortunately, the folks who need to hear most of that don't visit sites like this.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Tony, Maybe that is a blessing in disguise. What's the difference between a critic and a critical thinker? The thinking part. We all have the capacity to “rig” anything to get through an emergency. What is sad is when some think that method is an actual correct repair. The conscious individual will get through the situation and then fix it correctly as soon as possible.

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David Owner/Technician
Alberta
David
 

Jesse, i guess my memories of those years are not quite the same as yours. I saw lots of techs I would never have wanted near my vehicles or tools! I doubt the measure of an auto tech should be based upon such a thing as being able to torque a fastener close to specs without a torque wrench. The same goes for memorizing various specs that are well provided with a legitimate information…

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Bill Owner
Maryland
Bill
 

“I doubt the measure of an auto tech should be based upon such a thing as being able to torque a fastener close to specs without a torque wrench. The same goes for memorizing various specs that are well provided with a legitimate information provider.” Dave, Thanks for saying this. I would respect a tech that asks for the torque wrench and looks up the specs much more than the guy who has…

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Timothy Owner/Technician
Wisconsin
Timothy
 

That does not appear to be a great surface. Many of the new RMS requirements, going back for quite a while, have numbers that cannot exceed 10 RMS. Way back, when the 4.6L first hit the street, it required an RMS of 8. Ford just recommended replacement with new head castings instead of using an incorrectly smoothed head…

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David Owner/Technician
Alberta
David
 

Tim, I do not have a measurement of just what the Ra or RMS is on this particular cylinder head surface. I think just viewing the photos is not so accurate. I think many of us may be surprized to find most alloy cylinder heads need an RMS surface finish between 40 and 60. A 10 would be highly unusual. Cast iron heads are often in the 80-90 RMS range. My understanding of these surfaces is that…

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Bill Owner
Maryland
Bill
 

“Many of the new RMS requirements, going back for quite a while, have numbers that cannot exceed 10 RMS.” Tim, Without finding some factory manuals I really dont know how true that is. Fel Pro certainly does not require anywhere near that low of an Ra number. felpro​.​com/technical/tecb… That being said …. it is very easy to get an Ra 10 finish with any type of modern surfacing…

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Marlin Technician
Oregon
Marlin
 

Based on the photo of the comparator plate, this surface doesn't nearly meet the Ra requirement. Even if it did, it is unacceptable due to the shape of the roughness, which is troughs instead of random irregularity.

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David Owner/Technician
Alberta
David
 

Bill, thanks for chiming in again. I have no idea why this one has me so fixated. I should know better. LOL You and I have both likely seen a lot of things that do not conform to specs or conventional wisdom that worked just fine for a long time. I feel we are not really able to condemn the job done on the head in this instance which seems completely without specs and verification of surface…

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Timothy Owner/Technician
Wisconsin
Timothy
 

That number comes from one of the machinists' journals I used to read religiously, when I was doing a bunch of ‘heavy’ engine repairs. The number stuck in my head, because I had to install a couple of heads on a 4.6L, and wanted to know what the spec was at the time, because the results of the head machining looked rather rough compared to what the heads looked like when I removed them. The shop…

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David Owner/Technician
Alberta
David
 

Tim, I must say this has been a good one to think about. It shows us all just how much assumption we all make regarding various necessaries to do our work. It is of course incumbent on each of us to get the most accurate and up to date information and make our decisions accordingly. There are so many things we learn at the school of hard knocks and also a large number of things we seem to get…

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Danny Owner
Florida
Danny
 

I'm a 3rd generation Auto Parts and Machine shop owner, established since 72. I'm 44 and started in the family business at 15. I can say I have seen a lot and sometimes I haven't seen anything yet. Well, off to my opinion. First off operator needs practice; the sander needs a new belt and adjusts the surface level. In the '60s, my grandfather and my father would resurface with a VanNorman Broach…

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Mark Engineer
Colorado
Mark
 

Cody What a great discussion/thread with 53 replies so far. So much excellent information (with a few opinions). I was concise in my early response, “Nope”. My time is too stretched for a comeback and I am not 100 percent certain that it wouldn't work, but I'm also not 100 percent certain it would. As a teenager (50 years ago) I worked in a machine shop. Later as an automotive research engineer…

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Kevin Educator
California
Kevin
 

As Mark stated, GREAT DISCUSSION! A number of years ago I wrote a Subaru training program. Head gaskets and head gasket sealing are a huge issue so it was a significant part of the class and I investigated and researched the issue specifically and generically. I decided that only the best machine shops, with significant Subaru experience, should be trusted AT ALL with Subaru cylinder heads. I…

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Alex Diagnostician
Australia
Alex
 

Brilliant thread … u just can’t get this depth of info and experience in a class or in one shop! Thanks to everyone for generous info shares👍

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